In an internal combustion engine such as a gasoline engine and a diesel engine, carbon deposits called caulking may be formed inside the engine during use. Generation of caulking causes an insufficient cooling inside the engine or blocks a flow of the lubricating oil, which may bring various damages. Particularly in the engine provided with a turbo mechanism, caulking generated in a turbo bearing, a housing or an oil supply path is a problem. Moreover, caulking is more likely to be generated by using a lubricating oil exhibiting a low viscosity and an easy changeability to mist.
In order to prevent a change to mist and generation of caulking, the use of a lubricating oil having a low vaporizability is effective. As the lubricating oil having a low vaporizability for the internal combustion engine, a composition including a blend of a base oil of Group II or Group III in the API classification and a low viscous PAO has been proposed (see Patent Literatures 1 and 2).